Oblicz granice ciągów
a) [tex]a_{n} = \frac{n^{3}-n }{1-n^{2} }[/tex]
b) [tex]b_{n} = \frac{2n}{n+2} - \frac{n^{2}+1 }{n^{2}+n }[/tex]
c) [tex]c_{n} = (\frac{3n-1}{3n+1} )^{6n}[/tex]